By Irfana
B.Sc (Psychiatry Ward)
30 April 2022 -
Medically reviewed by
D. Pharm
How long does Prozac stay in your system?
Table of Contents

Prozac (Fluoxetine) stays in your system for 25 days after an individual stops taking the drug. However, the prescription drug is only 99%out of the system.

If a patient takes Prozac for more than 22 days, then specific metabolites are excreted into your system. These secretions will take around 22 to 82 and a half days to be eliminated from your body, depending on other factors.

80% of the drug is excreted through urine.

You can purchase Prozac online from a certified online pharmacy but it is recommended to get a doctor's prescription first.

Half-life of Prozac?

Half-life refers to the time taken by a drug to reduce the amount of active ingredients present in your blood in half. Fluoxetine has a half-life of roughly 2 to 7 days; however, norfluoxetine has a half-life of 4 to 15 days. Fluoxetine remains in the system for approximately 2 to 3 months after the last dose when nor-Fluoxetine is wholly eliminated.

Study On The Half-life Of Fluoxetine:

 A study done to find out the pharmacokinetics of Fluoxetine found that Fluoxetine is well absorbed after oral administration, has a high protein binding rate, and has a large distribution volume. The half-life of Fluoxetine is 1 to 4 days, while the half-life of its metabolite, norfluoxetine, is 7 to 15 days.

Fluoxetine interacts with several other medications. The blood concentrations of antipsychotics and antidepressants were enhanced when Fluoxetine was given repeatedly. (Altamura AC, Moro AR, Percudani M. Clin Pharmacokinet. 1994 Mar;26)

Another study was done on the half-life of Fluoxetine, and its metabolite nor Fluoxetine found that the half-lives of Fluoxetine and norfluoxetine were 11–16 hours and 21–29 hours, respectively. Even after a single fluoxetine dose, functionally significant blood concentrations of norfluoxetine were detected at 24 hours. Norfluoxetine accounted for the larger percentage of active substances in the bloodstream, as observed in people under steady-state settings. (Sawyer EK, Howell LL. 2011;88)

Factors That influence the Stay Of Prozac?

The stay of Prozac depends on various factors, such as how long you have been taking it? And how much have you been taking? Other factors that influence the stay of Prozac are,

  • Age
  • Sex
  • Body Mass
  • Genetics
  • Food Intake
  • Hepatic Function
  • Metabolic Rate
  • Urinary PH

The metabolites released when taking Prozac (known as norfluoxetine) will take 22 to 82 and a half days to empty the patient's system.

How Long Does Prozac Take To Work?

 The active ingredient, Fluoxetine, is absorbed in the gut after taking the drug. It is metabolized in the liver, where it is converted to norfluoxetine metabolites via demethylation processes.

Fluoxetine's mental health advantages, like those of most antidepressants, do not appear immediately after therapy begins. Some people may show changes as soon as two weeks after starting treatment, but it usually takes 4-6 weeks to manifest the total mental health benefits.

How Long Does Prozac Stay Hair, Urine, and Blood?

Prozac is not usually found in standard urine, hair, or blood tests. On the other hand, special test kits can be used to check for the presence of Prozac in various tissue samples.

Urine: Urine tests from Prozac users have revealed detectable levels up to 96 days after their previous medication. 

Blood: Blood samples from people who had been on Prozac for a long time proved positive for the drug even 96 days after they stopped taking it.

Saliva: There is inadequate evidence defining how long Fluoxetine can be found in the saliva due to a lack of study.

Hair: Fluoxetine is undetectable in hair samples. As a result, the drug in the hair has no detection time.

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